Electrochemical and morphological characterization of prefilmed aluminium brass

Materials Chemistry and Physics, 8 (1983) 337-348

ELECTROCHEMICAL PREFILMED

G.

AND

Centro

and

di studi

mica, O”

MORPHOLOGICAL

ALUMINIUM

BRUNORO’

0

Via

L.

Corso Received

P.

SPINELLl

sulla

degli

46,

“A.

Dacco”,

FERRARA

1982;

e lngegneria

TURIN

24,

Universita

di Ferrara,

lstituto

Chi-

(Italy)

dei Materiali

Abruzzi

8 November

OF

O”

Corrosione

di Scienra

Duca

CHARACTERIZATION

BRASS

Borsari

Dipartimento

337

accepted

Chimica,

Politecnico

di Torino,

(Italy)

6 December

1982

ABSTRACT

Electrochemical with

and

morphological

Benzimidazole-2-thioi

rious

plls.

tective

of

action

of

film.

between

mitation

layer

as

/ NTRODUCT The

inhibitor

cathodic

shown

in 0.1

the

immersion

in the

sodium

giving

rise

and

metal

seems

to be

current

density of the

for

oxygen

inhibitor

with is

resistance

brass

chloride

layer

temperature

film

never

the

Alum~nium

sodium

a surface

prefilming

that

of N

occurs,

a consequence

to

very

chloride

on the

solution,

localized

reduction.

interaction

is

for

va-

pro-

the

pro-

pH

of the

a uniform

attack.

responsible

of

good

increase

depends

to

prefilmed

solutions

An

inter-

a marked

A stabilization

ii-

of the

suggested.

I ON

protective

effectiveness

copper

and

copper

proved

the

practical

nium

film

made produces

of the

was

prolongued

surface the

of the

effect

It

Upon the

characterization

was

treatment

The

the

solution.

removal

oxide

prefilming

properties.

tectivity test

The

(BIE)

alloys,

of Benzimidazol

has

been

importance

of

e-2-thiol

investigated this

(BIE)

in a series

substance

as

as

an

of papers

a prefilming

inhibitor

for

(I-4)

which

for

Alumi-

agent

brass. Recently

tored

by

prefilming it was

(5)

treatment.

I ast

et ectrochemical a sol ution

growth

el lipsometry,

immersed

These

the

thus

of

the

individuating

Characterization

in an aggressive results

suggested

properties

containing

copper-inhibitor

of the

of

the

optimal

the

film

environment to extend films

film

was the

formed

during

experimental

properties also

and

Aluminium

was

conditions its

investigated

investigation on

prefilming

for

behaviour

the when

(6).

to morphological brass

moni-

by

and

immersion

in

BI E.

0

Etsevier Sequoia~~nted

in The N~therlaRds

338 This

paper

observations

reports

and

filming

temperature

EXPER

I MENTAL

The were The

electric

back

(0.25

Prefilming of

curves

were

thodic

branch

not

only

chloride

prefilmed

electrodes

The in

at

stirred

obtained tests

for

192

the

(5-6).

to evaluate

ratures.

These samples

of cast

n.

films

the

both

effect

by

SEM

of the

Aluminium

an

exposed

wire,

sealed

800

emery

electrodes

for

These

pre-

brass

surface

and

of 2 cm’.

J

in a smal

paper

and

which

had

been

curves

were

glass

then

alumi-

to

localized

at

at

desired

After

was

of nor-

prefilming,

the

in air.

sodium

chloride

25OC.

Anodic

to

those

tests

55O and

various

affects

obtained

were

the

with

performed

85OC

water

at

rest

at

polarization

substantially

the

amount

temperature

in distilled

on prefilmed

aspects

protective

proved,

started

solutions

in 0.1

same

in a neutral

at

and

ca-

nonin 0.1

with

non-

5S”

or

85’C

potentiai

and

were

which

were

192

hours

car-

.

samples

hours

N

BIE

prefilmed

were

made

chloride

The

the

85OC.

compared

pre-treated

-1

1 mV.s

adding

dried

at

with

range.

electrodes

of

prefilmed

were

for

the

tests

pH

and

in 0.1

prefilming

5 minutes

prefilming

and

traced

curves

same

55”

water

ef ectrodes

by

The

at

led

were

morphological

552

made

pH=7

rate

prepared

water.

were

since

in the

the

was

in distil

non-prefilmed and

in order

prefiimed

on

N sodium

with

bars

with

immersing

curves

observations

The

temperature.

ar,

a copper

polishing

tests

Polarization

0.1

particui

to obtain

through

solution

rinsed

9)

at

a scan

SEM

in order

considered,

N sodium

out

resin

by

some

7 and

5 minutes.

of cylindrical

to bi-distilled

was

electrodes

ried

BIE

but

prefilmed

for

such

electrode.

The

polarization 5,

In

out

included

BIE.

surface

(pH=3,

studying

account.

made

obtained

reagent

Cathodic pHs

the

by

tests.

into

cut

was

of

was

25 2 1 OC,

electrode

obtained

pm).

10W3M

grade

mally

were

preparation

na polishing

solution

taken

in “Epophix”

the

Surface

pure

was

connection

from

results

electrochemical

electrodes

embedded

tube,

by

the

at pH=3, of the

under

the

N sodium

attack.

same

time,

7 and

samples same

chloride

effectiveness the

electrodes 9 for

were

conditions.

very

at pH=7 at

scarce

the

at

room

to those

Moreover,

solutions

of prefilming the

compared

immersed

immersion were

various

tendency

made tempe-

of the

339 RESULTS

AND

1

Fig. rious

Dl SCUSS

shows

the

experimental

dium

chloride

electrodes

for

with

occur.

30

of

the

minutes.

increasing

It

of cupric

the

ions

can

potentials

be

solution nobler

as

seen

pH.

noble

a consequence

been

the

non-prefilmed to -0.201

no appreciable

variation

potential

va-

N so-

-0.136

electrode

of alloy

the

in 0.1

of the

(from

pH=7,

under

immersed

potential

values

of the

1 recorded,

corr

had

that

Above

values

(E

which

I ess

towards

the

that

rest

on electrodes

displace

We argued

presence

values

conditions,

markedly

V/SCE)

ION

were

due

did to

the

dissolution.

-0.10 _

* “/SCE

:

-0.15

A

_

\ ‘lo, O-0

\

-0.20.

-0

t -0.25.

Fig.

1.

pH:

0

*

Corrosion

some the

this

tests.

minutes

As

potential

very

Prefiiming of the

test

at pH=5

there

towards

positive

in 0.1

the

toward

to

25’YI

solution. seems

that

to be

values

of

cupric positive

ions

pH=3

no effect,

does

occur

addition,

an

was

5.10

-5

the

potential whereas (see

fig.

as

a function

of

electrodes;

at pH=3;

added

to the

immediate

A

non-pre-

For

M cupric

chloride,

without

of prefilmed at pH=?

and

example, an

cupric

potential,

solution

in

displacement

observed.

electrode

1).

N&I,

non-prefiimed

pH=3.

were

in a solution

affects the

at

ions

values

determined

N

l

+ 5. 10m4M CuC12 CuC12

cupric

containing

differently At

N NaCl

amounts

in 0.1

T=25%;

+ 5.10-‘M

in a sol ution

close at

of

brass

low3 M f3lE,

N NaCl

small

a result

immersion

potential

pH

in 0.1

reason,

electrode

in

electrodes

electrodes

PH

of Al uminium

ei ectrodes

non-prefilmed

For

9

potentials

prefiimed

filmed

7

5

3

ions

after

9 a small

is

30

electrode was

depending

electrodes

of

obtained. on the

I ess

noble,

displacement

340

I owering

The sing of

of cupric

the

been

film.

ions On

reported

filming stabil

electrode

other

previous1 may

effect

Figures

the

y (2)

be

show

the

various

pHs,

observed

that

the

polarization

for

the

first

for

the

curves

of part

the

of the

traced

a consequence increase and

explained

by

was

attributed

of the

in the copper

initial

potential alloys

to the

decrea-

protective

at

pH

7,

in the

presence inhibitor

the

adsorption

of the

polarization

curves

obtained

action which

has

of preor

by

its

oxide.

cathodic

both

on prefil curves

current

at pH=3

on copper

surface

at

values

the

simply

sol utions

smaller

as

hand,

on the

2 - 5

potential

concentration

the

agents, izing

of

density,

cathodic

med

for

and

the

non-prefilmed

prefilmed

compared

The

electrodes.

electrodes

to the

polarization.

in sodium It

always

can

be

present

non-prefilmed

ones,

noticeable

differences

most

chloride

at

least appear

at pH=7.

-0.5 _

-0.8

_ 0.1

Fig.

A.om-*

2.

Cathodic

solution (-----)

prefil

By curve low

of pH=3, med

anal ysing for

the

polarization.

non

polarization T=25OC: electrodes,

the

curves (-----I E

polarization

prefilmed

100

lo

on Aluminium non-prefi

corr

= -0.165

curves

electrode

I med

in aerated E

V/SCE.

in detail,

exhibits

brass

electrodes,

it can

a maximum

be

seen

current

0.1

corr

N NaCl

= -0.136

that density

V/SCE;

at pH=3

the

vat ue at

341

Fig.

3.

solution (-----)

Cathodic of pH=5, prefilmed

polarization

curves

( -_)

T=2S°C: el ectrodes,

\ “/SW

\

.

E

.

on Aluminium

non-prefilmed = -0.177

corr

-.

brass electrodes,

in aerated E

V/SCE.

corr

0.1 = -0.173

N NaCl V/SCE;

\

-0.5 _

: I I I1

-0.8 _

0.1

),.c,,,-~

100

lo

'r

Fig.

4.

solution (-----)

Cathodic of pH=7, prefilmed

polarization T=25”C: electrodes,

curves

( -)

on Aluminium

non-prefilmed E

corr

= -0.180

brass electrodes,

V/SCE.

in aerated E

corr

0.1 = -0.201

N NaCl V/SCE;

342 Tests peak

carried

of the

current

thodic

polarization

V/SCE,

which which

cess,

hydrogen

is

ions

by

by

is

been

even

in this

of

oxygen

occurs

at

more

is

the

not

under

potential

step

reduction

pH

affected,

and

control

appears after

and

action peak

while

on the

ions. at

that

seems

this

first

When

the

ca-

about

-0.4

a third

pro-

to be due

to

value.

reduction

vat ues

confirmed

controlled

protective

ions

substantially

negative

solution,

of cupric

diffusion

initial

cupric

the

reduction

to oxygen

an

the

to the

corresponding

to exert of

to

a diffusion

case

at

absence

ions

to be due

attributed

reduction

duction

cupric

increased,

seems

the

adding

density

has

Prefiiming shown

out

even

at pH=3,

on the

the

cathodic

discharge

prefilmed

as

it

is

curve.

Re-

of hydrogen

ions

el ectrodes.

-0.2

\ V/SCL

\ \ \ \

-0.5

\

.

\

-0.t I _

.

_ _

0.1

Fig.

5.

Cathodic

solution (-----)

trend. with can be

There

is a slight

be

close

to for

oxygen the

galvanostatic

conditions.

It

was

initiates

at

shown

tests

a potential

of

E

non-prefilmed

The

and first

whereas

carried

in aerated

polarization

which

one,

that,

for

densities.

reduction,

second

of

I ow

brass electrodes,

V/SCE.

curves

at

current

med

-0.190

cathodic

fexion

in a series

oxide

Ecorr=

the

I imiting

attributed

responsible

9,

on Aluminium non-prefil

electrodes,

7 and

very

curves ( -)

T=25%:

pH=5,

_ __

100

lo

P

polarization

of pH=9, prefilmed

At

A.,3,,-2

l

out

in the

solution

-0.45

V/SCE.

corr

two

of these of cuprous

at

-0.45

V/SCE.

strict1

y control

under under

test,

the

V/SCE;

have

reduction

reduction

appears

N NaCl

electrodes

then

one

0.1

= -0.203

two

This

reduction

processes

processes,

oxide

led

similar

seems was

to

shown

experimental of cuprous

343

-0.8

’ r

,,.~,,'2

Fig.

6 a.

solution

Cathodic of pH=7,

5 minutes, for

polarization T=2S°C: = -0.181;

E

5 minutesyrr

E

100

lo

curves

on Aluminium

brass

(-----)

electrodes

prefil

med

( -)

electrodes

pi-e-treated

in aerated

in

10F3M

BIE

in distilled

0.1 at

N NaCl 55’C

water

at

for 55OC

V/SCE .

= -0.203

cot-r-

- 0.8,

1

0.1

Fig.

6 b.

solution

’ r Cathodic of

5 minutes, at

85*C

p&7, E

for

A .cm-2

I

I

IO

100

pal arization T=X°C: = -0.214

Y?*&k&es,

curves

(-----) V/SCE; E

corr

on Aluminium

electrodes (------

= -0.192

prefiimed

1 electrodes V/SCE.

brass in

in3aerated 10

pre-treated

M BIE

0.1 at

N NaCi 85%

in distilled

for water

344 For to that

the

prefilmed

obtained

with

decreasing

of the

up to -0.6

V/SCE.

At smaller

pH=7

increasing V/SCE,

pH=9

the

wered

the

Figures polarization ced

on

water

inhibited.

sion

in

sing

the

which

10

7d,

indicates After

non-prefilmed of and

specimens did

not

two

of

cathodic than

prefilmed

curve

ViSCE,

potentials

the

are

for

It

for

ten

times

to disappear

more

almost

prefilmes

at pH=7. curves

polarization

are

tends

close

a sl ight

cathodic

difference

very

being

electrodes

electrodes

that

the

is

negative

the

prefil

be

seen

med

and

than

same.

electrodes

can

by

At is

that

lo-

starting

non-prefii

med

the

influence

electrodes

of

prefilmed

at pH=7,

are

ming

agent the

must

is

be

the

shown.

for

same

It

that

the

figures

tra-

the

catho-

immersion

in

appears

become

blocking

these

Cathodic

5 minutes,

cl early

curves

under

into

85OC

in a 5 minutes

show

Electron

temperature.

and

On

cathodic

formed

taken

Scanning

55O

also

the water

which

at

consisting are

in distilled

prefilming

reported.

temperature,

oxide,

the

that,

more

action

conditions.

and

more

cannot A

be

specific

account.

Microscope

observations

under

the

va-

conditions. b,

and at

c,

refer 55*

25O,

the

high of three

that

the

hours

the

surface

85’C,

and

of

specimens It

respectively.

it increases

aspect

the

brightness

area of

after

is

immer-

that

increa-

evident

covered

the

5 minutes

with

specimen

by

a surface

and

which

product is on1 y

magnifications. these

surfaces

with

temperatures,

for

surface

must

layer

immersion

specimens prefilmed present

to and

temperature,

very

192

of

electrode

temperatures,

tests

change

same

part

for

a pre-treatment

10 show

not

the

the

after

M BIE

at

show

surface

A comparison at

6b

prefilming

prefilming

evidenced

of -0.45

the

7a,

does

the

difference

This

kinds

compressed

chloride

experimental

-3

two

where

for

prefil

Figures

the

at pH=5

only

ones.

in fact

traced

ctose.

blank

7 -

for

more

and

to the

of the

potential;

value

the

Figs.

non-prefilmed

region

at

The

attributed

ter

the

very

increasing

rious

for

obtained

led

effect

values

N sodium

curves

distil

density

curves

in 0.1

dic

current

curves

6a

the initial

far

are

electrodes, the

potential

electrodes

curve

during

cathodic

is

cathodic

density

potential

down,

non-prefilmed

on the

the

the

current

those

the

-0.6

from

the

than

electrodes,

appeared at

any

in 0.1

the

attack

to be

three even

those which be

of

no surface attributed

N sodium highly

were

immersed

in distilled

modification to

chloride

corroded,

temperatures if they

samples

maintained observed

the

inhibitive

at pH=?, Fig.

occurs,

the

8,

while

their

initial

at high

waFig.

species. surface the

of

surfaces

brightness

magnification.

7d

7c

Fig.

7.

SEM

10-3M c)

prefilmed

at

85OC

slight

in any

The to

where is

10e3M

the

shown.

Aluminium

brass

prefilmed

85OC

for

in

5

all

surface can

time

min.;

after

simple of

of be

test,

specimens:

lo-

3 M

d)

pre-treated

a seen

specimen that

the

fig.

BIE

a)

at

prefilmed

55OC

for

in

distilled

to

552

in

5

min.; water

solution,

25°C

was

observed,

fig.

samples

up

9a.

leading

Prefil

prefilmed

hours,

ming at

85OC

to

at

a the

55OC

did

forma-

resulted

not

present

85OC

did

fig.

10,

9b.

immersion oxides,

in

distilled is

pre-treated after

test

products, and

protective

the at

corrosion

this

that

in

prefilmed

resistance,

formation

It

of b)

immersion

distributed

evidence

the

at

specimens

corrosion

the

4000)

min.;

BIE

the

uniformly

at

5

min.

on

better

(X

for

prolonging

attack

lead

25OC

in 5

attack of

a

at

for

By

tion

micrographs

BIE

192

given for

hours

water

5

in

the

at

and

photograph

minutes

immersion

55’C

in in

distil the

0.1

of led

water

N

sodium

at

not

85°C

chloride

346

Fig.

8.

SEM

immersion

micrograph

in 0.1

solution

at

pH=7,

however

it

is

The test pH=3

cl early

of pH=3

samples, was

of

non-prefilmed

is

higher

compared

and

9,

attack,

after

not

as

of by

marked

as

to the

prefil

film

formed

the

carrying

only

slightly

Even

in the

this

out smaller case

brass

after

192

hours

med at

non

of the

samples,

specimens. 25“C

hours than

pre-treated

was

also

immersion

that

experiments.

observed

solutions

considered

on the

at pH=9

in At

non-pre-

a moderate

at-

test.

9b

9.

SEM

5 minutes, a)

on the

192

9a

Fig.

Aluminium

of pH=7.

attack

appeared.

obtained

340)

solution

effectiveness

a generalised

filmed tack

the

protective

solutions

(X

N NaCl

prefilming

micrographs

after

552

hours

temperature

(X

340)

of

immersion 25°C;

Aluminium in 0.1

b) prefilming

brass

N

NaCl

prefilmed solution

temperature

85’C.

in

10

of pH=7:

-3

M BIE

for

347

Fig. at

10.

SEM

85OC

lution

for

micrograph

5 minutes

(X

and

350)

of Aiuminium

subsequently

brass

immersed

pre-treated

for

192

in distilled

hours

in 0.1

water

N NaCi

so-

of pH=?.

CONCLUSIONS The ments

overall

containing

protective

chloride

pH

10

that

the

the

in neutral

of

seems

I ocal

attacks

ized As

far

that

the

films

protective

pH

a duration

5 minutes

prefilming of

action

ceases

numerous

the

after

markedly

solution.

film

192

brass,

lasts

It

hours.

smaller

In for

Even

than

acidic

a very for

that

so-

whose

temperature.

test

of the

experi-

in a aqueous

on aluminium

the

on the

of the

of

I ayer

increasing

completely

have

results

treatment

depends

and

the

a surface

with

resistance

as

tal-inhibitor The 500

layer,

by

were

higher

observed

that

due

hours), stabilizing

shown

by

I imits

course

it

interaction

of BIE

on the

protective

suggests

that

it and means

the

to an

compound the

as

mechanism

strongly

surface

in the

uniformly

protective

film be

film,

of the

is

evidenced

is

concerned,

immersion by

the

in the

fact

that

aggressive

in no case

observed.

adsorption

fact

(over

surface

the

may

the

the

to occur

the

effect

viously

produces

minutes)

from

a prefilming

increase

protective

solution,

through

30

out

solutions.

Removal

This

that

environments,

(about

values,

comes

M BIE,

film

containing time

dicate

-3

characteristics

shown

short

which

indicates

performed,

lution

was

picture

by

can

cathodic between metal

also

be

action,

at

the

inhibitor

lowering

of photo-effects

its

or

current the

considered at

measurements

density

oxide.

for and

The

tests

oxygen the

reduction.

metal

formation

in-

surface, of a me-

(7,8). pH=7,

undergoes electronic

electrochemical

inhibitor

on the

least

the

an

lasts

for

a very

interaction

with

conductivity, (5).

as

is

long the was

time oxide

pre-

348 ACKNOWLEDGMENT The authors tal

have

appreciated

the help

of Dr.

R.

Nagliati

with

the experimen-

work.

REFERENCES 1

G. TRABANELLI, Korros.

2

F.

F.

ZUCCHI,

G.

BRUNORO,

V. CARASSITI

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ZUCCHI,

G.

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ZUCCHINI

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2,

834

(1977). 3

F.

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4

G.

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M.

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G.

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, M.

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G. BRUNORO,

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SPINELLI,

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3l,

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MAJA,

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